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A R Y EC R IB TO O OBSERVA August 2000, Number 30

Observing Proposal Reminder: The next proposal deadline is October 1, 2000. Please make a note to get your proposals for observations using the Arecibo Observatory facilities submitted by that date.

such as heat transport, momentum flux and the small magnitude of the vertical D-region Vertical Wind Measure- and chemical mixing. However, its mea- wind. Although previous measurements ments at Arecibo surement in the mesosphere (60-100 km of vertical winds were made by Gangu- Qihou Zhou altitude) is very difficult because of the ly (Geophys. Res. Letters, 7, pp. 369- region’s general inaccessibility to many 372, 1980) at Arecibo, an integration ertical atmospheric motion is im- techniques (such as balloons and aircraft) time as long as 45 min was needed due Vportant for a number of reasons to the poor signal-to-noise ratio (S/N). Such a long integration time does not allow one to study gravity waves hav- 95 (a) 95 (b) IPP=4 ms IPP=1 ms ing a period less than an hour, which dominate the gravity wave spectrum in 90 90 the mesosphere. Here we report a sig-

85 85 INDEX 80 80 D-Region Vertical Winds ...... 1 Telescope News ...... 2 75 75 Altitude (km) NAIC Director’s Comments ...... 3 Solar System Studies ...... 5 70 70 Space and Atmospheric Sciences .... 6 Radio Astronomy Highlights ...... 7 65 65 Square Km Array Workshop ...... 12 -10 -5 0 5 10 -10 -5 0 5 10 Topside Ionosphere Workshop ...... 13 Vz (m/s) Vz (m/s) Pulsar Workshop ...... 13

Fig. 1: (a) Vertical velocity at 12:30 LT on November 25, 1999 by using a 4 ms inter-pulse-period Recent Colloquia ...... 14 scheme. The integration time for this plot was 64 seconds and the number of pulses used to obtain each Peeps into the Past...... 14 power spectrum was 128. (b) Vertical velocity around 12:30 LT, October 2, 1999 by using a 1 ms inter- Comings and Goings ...... 14 pulse scheme. The integration time was 8.5 min. The number of pulses used for the power spectra was Of General Interest ...... 16 256. (Courtesy Qihou Zhou) Job Opportunities ...... 17

The NAIC is operated by Cornell University under a Cooperative Agreement with the National Science Foundation. Upward Wind Measured by the Arecibo ISR sis of the incoherent scatter spectra will allow the determination of ion-neutral collision frequency, temperature and 90 negative ion composition. The short in- 85 tegration time achieved by our 4 ms IPP scheme is not only a matter of time reso- 80 lution but often a matter of feasibility. For instance, our results show that the 75 Doppler broadening of the power spec- Altitude (km) tra due to vertical bulk motion averaged 70 over 20 minutes is of the order of 12 Hz for a probing frequency of 430 MHz. 65 Average Vz (m/s) This broadening is comparable with the 9 101112 incoherent scatter spectral width below 75 km thus rendering the results derived LT (Nov. 25, 99) from the spectra averaged over 20 min -6 -4 -2 0 2 4 6 Upward velocity (m/s) inaccurate. With a soon-to-be installed Fig. 2: Vertical velocity measured by the Arecibo incoherent scatter radar on Thanksgiving (11/25), second 430-MHz feed and an existing 1999. The average velocity shown on the right was averaged over 08:25-12:54 LT. The two black lines VHF radar at the Arecibo Observatory, indicate the region of valid measurements. (The color version of this plot can be seen in the associated the technique used here will be signifi- journal article–Zhou, Geophys. Res. Letters, 27, pp.1803-1806, 2000–or the web version of this newslet- cantly improved. It will also be possible ter available at http://www.naic.edu.) (Courtesy Qihou Zhou) to study diverse topics relating to the dy- namics, structure and composition in the D-region including heat flux, momentum nificant improvement in the measure- mentioned above. For typical Arecibo transport, composition of negative ions ment of the mesopause vertical wind conditions, the noise level at the altitudes and interactions of gravity waves with using the incoherent scatter radar (ISR) of interest can be easily 30 fold greater turbulent layers. We expect an active D- technique. with the 1 ms IPP than with, say, a 4 ms region research program in the coming IPP. The 4 ms IPP scheme has the dis- years. In the D-region/mesosphere, we mea- advantage that the unaliased measure- sure the Doppler shift of the plasma, ment bandwidth is correspondingly This article is adapted from Zhou, Q. which moves with the neutral atmo- narrower, thus lowering the altitude cov- H., Geophys. Res. Letters, 27, pp.1803- sphere, by taking the Fourier transform erage by about 8.5 km. For high-reso- 1806, 2000. Interested readers can either of sequentially transmitted radar pulses. lution vertical wind measurements it is refer to the GRL article for details or This is the so-called pulse-to-pulse FFT necessary to sacrifice altitude coverage contact Qihou at [email protected]. (PPFFT) technique. Ganguly used an for accuracy. Figure 1 compares the ver- inter-pulse-period (IPP) of 1 ms, which tical velocity profiles obtained using the Telescope News provides a 1 kHz bandwidth for the spec- 1 ms and the 4 ms scheme, respectively. tra measured. Although the ionospheric Below 90 km, the 4 ms IPP scheme with Don Campbell return from the F-region is folded into 1 min integration is clearly far better than Pointing and Platform Stability: New the D-region measurements for the 1 ms the 1 ms IPP scheme with 8 min inte- pointing observations were made in Feb- scheme, the F-region spectra will essen- gration. Figure 2 shows several hours ruary. The resulting pointing model has tially be flat within the 1 kHz spectral of data derived from the 4 ms IPP an rms error close to 6 arc sec for all sys- width, which thus appears only as noise. scheme. An analysis of the data sug- tems above 1 GHz. Due to the hard work One can typically obtain useful D-region gests the existence of a turbulent layer of Phil Perillat (NAIC) the platform tie- spectra up to about 98 km, above which around 80 km and non-linear wave-wave down system is now in operation keep- spectral aliasing becomes too severe to interation below 80 km (see Zhou et al., ing the mean height of the platform very get useful information. Geophys. Res. Letters 27, pp. 1803- stable so that daytime pointing accuracy 1806, 2000). Although the 1 ms IPP scheme pro- is comparable to that obtained at night. vides almost the largest bandwidth for The reason for the high accuracy of Receivers: The new 1.7 GHz to 3.0 GHz the PPFFT technique for the Arecibo vertical wind discussed here lies in the receiver is now available for use. How- ISR, its drawback is the increased noise dramatic improvement in the S/N of the ever, the system temperatures for the two from the F-region ionospheric returns as incoherent scatter spectra. A full analy- polarization channels need to be im-

August 2000, Number 30 2 NAIC/AO Newsletter NAIC Director’s Comments Paul F. Goldsmith, Director NAIC recently returned from a very stimulating sabbatical year spent primarily in a variety of European institutions, Iincluding the Cavendish Laboratory, University of Cambridge (UK), the Max Planck Institute for Radio Astronomy, Bonn (Germany), the École Normale Superieure, Paris (France) and the Osservatorio di Arcetri, Florence (Italy). In between, I spent intervals in Ithaca and Arecibo. I was working on data from SWAS satellite, but also on 21-cm absorption line data from Arecibo obtained with Di Li (Cornell). The two ended up having an interesting potential connection in terms of molecular cloud structure, but that’s another story. While Don Campbell was Acting Director of NAIC during this interval, I did assist in a variety of administrative tasks. In particular, I am pleased to announce that Dr. German Cortes will be joining the staff in Ithaca as a Senior Research Associate. German is an expert on the electromagnetics of antennas and will be working on a number of projects to improve performance of the Gregorian system, as well as in the design of focal plane arrays and other advanced systems. Other new staff members at Arecibo include Jeff Hagen, who has already made real contributions to real-time data acquisition software. We hope to have a new receiver engineer on board by the end of the year to work with Lisa Wray, another new electronics department staff member, to work on the ever-growing (but still not big enough) stable of receivers. Otherwise, I can announce that the upcoming Arecibo Users and Scientific Advisory Committee (AUSAC) meeting will be November 13-14. Dr. Tom Troland has agreed to be the Chairperson Designate, while Dr. Phil Myers is this year’s Chair following his work putting together the very helpful report from last year’s meeting. The Visiting Com- mittee meeting will be November 15-17. Dr. Jacqueline van Gorkom will be the Chairperson of this year’s meeting. This format follows those of recent years, with visitors staying at Hotel Vistamar in Quebradillas. Our plans to build additional VSQ units to allow housing of committee members on site have progressed, but no construction has begun due to financial constraints. There is a very nice set of drawings for new unit, but we will have to await getting some supplemental funding to make this a reality. There are some real possibilities happening in the near future, so stand by for developments. In a recent visit to Arecibo, I was impressed with progress on central aperture closure, the active tidedowns, and the expansion of the cafeteria. Not so visible, but very significant was the newly constructed building now housing the transmitters moved from Los Canos heating facility. I can see great potential with the Wideband Arecibo Pulsar Processor (WAPP), the active tertiary control system, and newly installed 327 MHz receiver system. We await delivery of the VLBA4 recording system within next few months, as it has finally been built and only needs to be tested. The surface repair effort is nearly completed, and an extremely important measurement effort is just about to start. This is vital for future projects! Also, there have been enormous improvements in the internal and external networks, signifi- cant enhancements of telescope and analysis software, and very successful outreach efforts with teacher training work- shops. It may be that a few months away makes all this work more evident than if one follows it more closely, but in any case, I am really excited about the accomplishments and new potential and look forward to resuming work with staff on ensuring that the ongoing and new projects come to fruition. proved. The temperatures at zenith for Work has been proceeding on a using the active tie-down system, L-band the two channels are 35±5 K and 37±4 cooled 327 MHz system for the Grego- spectral line observations can be done K. The range is due to a systematic rian dome. All the components are com- during daylight hours. However, due to change in the temperatures across the pleted and installed in the dome. Testing interference from the currently active band. There is a 1 K increase in the tem- of the system is currently underway. sun, wide-band observations should be peratures out to 15° zenith angle and a However, the RFI environment is clear- avoided between about 10:00 AM and further 5 K increase out to 20° zenith ly challenging and a variety of mitiga- 3:00 PM local time. Narrow line-width angle. The sensitivity at zenith is close tion approaches will be studied. observations can be made during this to 7 K/Jy at the band center, decreasing time. General daytime RFI levels are Spectral Line Observations: With the by about 25% at 20° zenith angle. higher than at night. stabilization of the mean platform height

August 2000, Number 30 3 NAIC/AO Newsletter VLBI: The VLBA4 VLBI recorder http://www.naic.edu/~pulsar/ face will proceed in two stages. In the which has been on order for over a year machines.html first stage the positions of about 2,000 is finally in the acceptance test phase. targets distributed over the surface will The NAIC-developed Wideband Tests were carried out at the manufac- be measured using photogrammetry and Arecibo Pulsar Processor (WAPP) is turer’s facility in early August and some the reflector surface “set” by making ap- now in routine use and available to tele- corrective work was found to be need- propriate adjustments to the lengths of scope users thanks to the hard work by ed. NAIC is being assisted by Haystack the 1,800 tie-down cables that connect Bill Sisk, Andy Dowd, Jeff Hagen,and Observatory staff in the testing, and we the reflector’s cable support system to Dunc Lorimer (all NAIC). The WAPP’s are very grateful to them. As soon as the concrete blocks in the ground. These tie- current specifications can be found at: recorder is received at Arecibo it will be down cables define the overall spherical http://www.naic.edu/~wapp. The capa- integrated into the system and test ob- shape of the reflector and adjusting them bility to do on-line folding is currently servations taken and correlated. Once the will take out surface errors at about 8 m being developed. Watch these pages for system’s performance is verified it will scales and larger. Once the panel adjust- more details. be made available to observers. ment studs are repaired a target will be Graphical User Interfaces (GUIs) and attached to each of the 38,000 panels and Those wishing to use the 305-m tele- Remote Observing: GUIs are now in panel-to-panel errors removed based on scope for VLBI should submit their ob- regular use for spectral line and pulsar another set of photogrammetric measure- serving proposals to the appropriate observations thanks to Dunc Lorimer. ments. NAIC has purchased a photo- VLBI organization, depending on The advent of the GUIs combined with grammetry system and Lynn Baker is whether Arecibo is to be used in con- the recent installation of a T1 (1.5 Mbits/ using this system to measure the target junction with the VLBA, the European sec) internet link to the observatory positions with an expected accuracy of VLBI Network (EVN) or the Global makes remote observing practical. Pul- about 1 mm using photos taken from the Network. Such proposals should specif- sar search and timing observations have tops of the three towers. Initial test mea- ically justify the inclusion of Arecibo in been conducted remotely for some time surements were made in late July. the array, and NAIC would appreciate and are routinely successful. However, receiving a copy of the proposal. Arecibo The aim of the primary surface re- there have been some problems related will coordinate the allocation of 305-m setting is to bring the rms surface accu- to the interaction of the remote observer telescope time with the relevant array racy as close to 2.0 mm as possible. This with the telescope and the telescope op- scheduler(s), but as we are often com- will allow good aperture efficiencies for erator. Based on these experiences, more mitted for support of non-VLBI time wavelengths as short as 3.5 cm. rigorous protocols for remote observing critical observations NAIC cannot abso- are now in effect. As a result, remote Primary Reflector Aperture Closing: lutely guarantee that it will be able to observing for both pulsar and spectral For those readers who have wondered support any given experiment. Propos- line observations are now possible. De- why there is a large hole on the center of als requiring the use of Arecibo with a scriptions of the GUIs and a discussion the primary reflector you need wonder small ad hoc set of telescopes should be of the remote observing protocols can no longer! It is being filled in. Original- submitted directly to NAIC. These pro- be found at: http://www.naic.edu/~aoui ly the area at the center was left open to posals will undergo NAIC’s normal re- and also on page 17 of this Newsletter. facilitate lifting large items to the plat- view process. form using a winch. However, it is equiv- Primary Reflector Setting: The 305-m Pulsar Observations: NAIC is pleased alent to about 1% of the effective primary reflector was last set in 1986 to to announce that agreement has been collecting area and while closing it with an RMS accuracy of 2.2 mm. Over the reached with Don Backer (University of panels will not have an appreciable ef- intervening years the surface setting ac- California at Berkeley) to make the fect on the gain it should reduce system curacy has degraded especially in the Arecibo-Berkeley Pulsar Processor temperatures by 2 to 3 K. Twenty four central area of the reflector in which over (ABPP) and the Berkeley-Arecibo- 25 ft × 3 ft panels were designed and three hundred panels were damaged dur- Caltech Swift Pulsar Instrument (BAC- constructed under the direction of José ing the telescope’s upgrade. Last No- SPIN) user owned/public access data Maldonado and will be installed by the vember, NAIC began the task, under acquisition instruments. This means that end of August. José Maldonado, of repairing and paint- any observing proposal can request use ing all the hardware in the primary re- Dual Beam 430-MHz Transmitting of these machines. Details of their per- flector. This has now been completed System: The major hardware compo- formance specifications can be found at: except for the repair/replacement of the nents of a 430-MHz transmitting capa- approximately 30% of the 38,000 panel bility in the Gregorian Dome should be http://astro.berkeley.edu/~mpulsar/bpp/ adjustment studs which are corroded. in place by early fall of this year. Slotted bpp.html The measurement and setting of the sur- waveguide was installed along the feed –or–

August 2000, Number 30 4 NAIC/AO Newsletter arm in late 1999. Jon Hagen (NAIC) de- polar region of Mercury signed a new collector and turnstile have produced high which were fabricated in NAIC’s Ithaca quality images with res- laboratory. Most of the waveguide from olutions down to 1.5 km the feed arm to the receiver room in the (see Figure 4) an order dome was installed in early August un- of magnitude improve- der the direction of Felipe Soberal ment over the pre-up- (NAIC) and the platform maintenance grade images. The new crew. Full operation will depend on suc- images have revealed cessful system tests and modifications many previously unseen to the data acquisition and real-time anal- features including some ysis software to handle the additional at latitudes as low as 72° channels. N. Considerable fine structure can now be seen for the larger fea- Solar System Studies tures including effects Don Campbell related to crater central peaks and, for craters While there has been considerable ob- away from the pole, the serving activity over the past six months, concentration of “ice” primarily of near-earth asteroids and Fig. 3: These radar images of asteroid 216 Kleopatra were obtained in the permanently Mercury, most of the excitement has cen- at Arecibo on November 7, 1999 about an hour apart. The scale bar shaded equatorward tered on the results of the analysis of ob- (lower left corner) is 100 km. The top row are the data, which are portion of the crater servations taken in the summer and fall delay-Doppler images with range increasing down and frequency in- floor and interior rim of 1999. Delay-Doppler images of the creasing towards the right. The middle row shows delay-Doppler im- ages computed from the shape model, and the bottom row are “ordi- wall. These results are mainbelt asteroid 216 Kleopatra ob- nary” plane-of-sky images produced by the model. The model was placing very stringent tained in late 1999 by Steve Ostro (JPL) produced from a total of 12 delay-Doppler images on four days, along constraints on theoreti- and collaborators were used by Scott with the results of an earlier stellar occultation. (Courtesy Mike Nolan) cal scenarios for the Hudson (Washington State University) to generate a detailed shape model for Kleopatra, the first main belt asteroid to higher resolution observa- be imaged from the earth. Its dimensions tions from Arecibo by John are approximately 217 km by 94 km by Harmon (NAIC) and col- 81 km. As discussed in the paper pub- laborators showed that lished in Science (5 May, 2000) the high- most of the radar echo orig- ly elongated “dogbone” shape of inated from reflections Kleopatra (see Figure 3—“Dream on from probable ice deposits Canis Major” was the caption to the im- on crater floors. Ice is the age in the New York Times) indicates most likely condensed vol- that the asteroid may have resulted from atile based on its abun- the collision of two or more fragments dance and the similarity of of a precursor asteroid’s disrupted me- the radar echoes to those tallic core. The derived surface proper- from the (water) ice surfac- ties of Kleopatra are consistent with it es of the icy Galilean sat- having a regolith with a metallic com- ellites of Jupiter. However, position and a porosity similar to that of there is the possibility that the lunar regolith. some other condensed vol- The discovery of possible polar “ice atile such as sulphur is re- caps” on Mercury with the Goldstone sponsible for the very Fig. 4: Radar image of the north polar region of Mercury from and Arecibo radar systems in 1991 initi- strong radar echoes. New Arecibo S-band observations by J. Harmon and M. Slade on July ated numerous studies of the stability of observations in 1998 and 25-26, 1999. The resolution is 1.5 km and the image measures 450 ice near the planet’s poles, both sub-sur- 1999 by Harmon, Phil Pe- km on a side. The bright features are thought to be ice deposits in face ice and ice on the permanently shad- rillat (NAIC) and Martin permanently shaded crater floors. The pole is marked by the asterisk ed floors of impact craters. Subsequent Slade (JPL) of the north slightly left of center. (Courtesy John Harmon)

August 2000, Number 30 5 NAIC/AO Newsletter deposition and maintenance of ice at the have working systems to un- 110 poles of Mercury and will probably re- dertake such studies in the fu- quire some reevaluation of the current ture. thermal models. We supported various 100 In the summer of 1999 Don Camp- World Day experiments this bell (NAIC), Greg Black (NRAO) and period, such as the April Wide 90 John Harmon detected the “ice” depos- Latitude Substorm (WLS) Altitude [km] its at the north pole of Mercury with study and Plasmaspheric Ob- Arecibo’s 70 cm wavelength radar sys- servations of Light Ions in the 80 tem. Most of the theories to account for Topside and Exosphere (PO- the unusual radar backscattering prop- LITE) in June, and an F-region 110 erties of ice in the solar system are based “baseline” study including ion on internal scattering within the ice and vector velocities in July. Oth- require the ice to have a very low loss er more specific experiments 100 for the propagation of radio waves. This that took place in July were the implies that the ice must be at least sev- tidal ion layer studies of Zhou 90

eral wavelengths thick so a detection at and Jonathan Friedman Altitude [km] a wavelength of 70 cm may be placing a (NAIC), vertical wind mea- lower limit on the thickness of the de- surements by Zhou, and the 80 posits of several meters. Further model- topside observations of Apon- ing based on the Goldstone Solar System te et al. (NAIC). 23:00 00:00 1:00 Radar’s 3.5 cm detection combined with Local Time [AST] Arecibo’s 13- and 70-cm results may fur- ther constrain the scattering process and K Resonance Lidar Work Fig. 5: Simultaneous potassium (upper) and sodium (lower) the thickness of the deposits. During the months of April concentration profiles taken during the night of 28-29 May. and May, Mats Rova and Ulla The time scales are adjusted so as to match. Peak K concen- Johansson, undergraduate en- trations are over 100 cm-3 and Na over 5000 cm-3. (Courtesy Space and Atmospheric Sciences gineering students from Umeå J. Friedman) Craig Tepley and Mike Sulzer University in Sweden, worked on the lidar telescope control Friedman for a week-long observing run, avid Meisel (SUNY Geneseo) and hardware and software that will be nec- the goals of which were to make simul- D Joe Geddes (Penn State) were here essary for pointing and steering in order taneous sodium and potassium measure- in early April and Meisel returned in late to make measurements of middle atmo- ments and to get the temperature July to search for optical signatures of spheric winds. They wrote the neces- profiling system operational. After dodg- micro-meteors. It is believed that a rel- sary software for both direct control as ing bad weather for two nights, they atively “constant” flux of such meteors well as control using inputs from an ex- plays a critical role in metal ion layer ternal program. They also imple- formation in the lower ionosphere. For mented the built-in encoder this study, Meisel brought two detector hardware for monitoring the tele- packages to attach to the back ends of scope positioning. We were two of our telescopes mounted on the pleased with the results they pro- roof of the Lidar Lab. Separate photo- duced over a very short period of multiplier tubes, sensitive to different time and expect to begin using their parts of the optical spectrum, were gat- additions soon. ed with timing signals from the 430 MHz radar to correlate the observations made During the week of May 22, with both instruments. John Mathews John Walling of Light Age, Inc. (Penn State) and Qihou Zhou (NAIC) provided a service visit to tune up were involved in the radar measure- the performance of the alexandrite ments, which are described elsewhere. laser used for the potassium lidar. The mating of Meisel’s equipment to our Following this successful service telescopes initially required many hours call, Steve Collins (Cornell) and Fig. 6: Mean mesopause temperature (thin line) and po- of machining, which was expertly done Shawn Allison (a REU summer tassium concentration (thick line) profiles for 5-6 July. by Raúl García (NAIC), but we now student from Penn State) joined (Courtesy J. Friedman)

August 2000, Number 30 6 NAIC/AO Newsletter achieved three nights of simultaneous High altitude ionospheric data from the recent solar storm operations. 2000 July 16 02:45:40 UT (Jul 15 22:45:40 AST) 2016 km Figure 5 shows simultaneous Na and 6000 All temperatures 2500K Data K data taken the night of 28-29 May. In 5500 Ne = 2900 cm-3 Theory spite of the different resolutions (4 min- 5000 utes and 300 m for K, 30 seconds and In this experiment using a fast-sampling data-taking 4500 37.5 m for Na) it can be clearly seen that system originally intended for solar system radar the layers behave similarly. Besides the 4000 studies we see the entire incoherent scatter return, the narrow ion line (normally all we look at), and the layer enhancement between 2330 and 3500 wide electron line (normally ignored). We can calibrate midnight, weaker features, such as the 3000 the ion line using an ionosonde to get the electron layers that broke off the bottom side of density, but one benefit of this measurement is that 2500 the enhanced layer and off the bottom we get the density (very low in this case) either from of the main layer around midnight, also 2000 the ratio of the power in the two lines or from a complete least squares fit. Calibration with an demonstrate similar behavior. 1500 ionosonde often fails during the chaotic conditions Temperature profiling proved more 1000 of a strong solar storm. difficult, but the technical difficulties 500 have to a great extent been resolved. On 0 July 5 Friedman repeated the tempera- 0 0.5 1 1.5 2 2.5 ture operations. Figure 6 shows the mean Frequency (MHz) temperature and density profiles of the layer for the night of 5-6 July. Three- Expanded frequency scale for the ion line frequency-mode observations on the x104 night of July 24-25 are presently being 20% H+ Data 1.2 + analyzed, but they have provided the 80% O Theory necessary calibration of the system in The electron temperature is set by the shape of the 1 order to be able to analyze the earlier re- electron line; the shape of the ion line contains the ion composition information, which in this case shows high sults. The low mean mesopause temper- O+ densities where the value should be close to zero. 0.8 ature, 160 K at 99 km, is not inconsistent The storm has changed the normal state of the with observations made during the Jan- topside over Arecibo (diffusive equilibrium with the uary 1993 10-day World Day (see Zhou 0.6 plasmasphere) to a non-equilibrium condition where the et al., J. Geophys. Res. 102, pp. 11,507- ionosphere is outflowing. This condition is what we would normally expect at high latitudes (i. e. the 11,519, 1997). 0.4 polar cap).

Relative spectral power density0.2 Relative spectral power density ISR Electron Line Measurements

During test observations for the imple- 0 mentation of new data taking software, Mike Sulzer (NAIC), Sixto González 0 10 20 30 40 50 60 (NAIC), and Richard Behnke (NSF) Frequency (KHz) were treated to an unanticipated and Courtesy Mike Sulzer Fig. 7 welcome event. Recent efforts to im- plement the capability to measure the time-resolution polarimetric studies of electron line of incoherent scatter, ob- Radio Astronomy Highlights millisecond pulsars. served only a few times in the last 30 Chris Salter years, encountered a huge solar storm. In contrast to most other radio sourc- Figure 7 explains the unusual conditions es, pulsars are often highly linearly po- that were seen in the topside of the ion- Pulsar Research larized, with the degree of polarization osphere and how useful the electron line Michael Kramer & Ingrid Stairs (Jodrell decreasing with increasing frequency. measurements are in such a situation. Bank), Kiriaki Xilouris (UVA), Don The sweep of the position angle seen Backer (Berkeley), David Nice, Eric across pulses of slowly rotating pulsars Splaver (Princeton), Shauna Sallmen can be successfully explained by a ro- (Berkeley) & Steve Thorsett (Santa tating-vector model originally proposed Cruz) are using Arecibo to carry out high by Radhakrishnan & Cooke in 1969. In

August 2000, Number 30 7 NAIC/AO Newsletter this model, the observed position angle itoring this pulsar is a projection of the magnetic field line with the Green Bank direction onto our line-of-sight cutting 140-ft and Jodrell through the emission cone. Millisecond Bank 76-m tele- pulsars have much shorter spin periods scopes since 1995, (P ~ ms vs. s) and weaker magnetic fields and recently discov- (B ~ 108 G vs. ~1012 G) than their slow- ered that it has suf- er counterparts. Thus these pulsars have fered 5 period a very open field geometry and a much glitches in the past 3 smaller light cylinder. Any emission cre- years! By compari- ated close to the surface of the neutron son, only 3 other pul- star will already be at a significant frac- sars have had more tion of the millisecond-pulsar light cyl- than 3 glitches ob- inder radius. The characteristics of their served, and two of emission regions may therefore be dif- those are the Crab ferent from those of slow pulsars, and and Vela pulsars, polarimetry is the best diagnostic for in- studied over 30 vestigating this possibility. years! Previous studies have already dem- Zepka et al. onstrated very clearly that polarization found the pulsar to characteristics of millisecond pulsars (or be highly polarized recycled pulsars, in general) indeed ap- at 1400 MHz, but de- pear to be different. Many objects show polarized at 430 Fig. 8: The full-polarization integrated pulse profile for PSR J2317+1439 distorted position angle swings which are MHz, possibly due to at 430 MHz. The measurements were made with the Princeton Mark IV. In difficult to explain by a rotating vector propagation effects. the top frame, the solid line is total intensity, the dashed line linear inten- model. However, these previous studies Camilo et al. recent- sity, the gray line circular intensity. The dots in the lower frame represent the position angle of the linear polarization. (Courtesy Michael Kramer) were limited to strong sources in order ly undertook a high to obtain reliable polarization informa- frequency-resolution tion. For the new Arecibo observations, 430-MHz observa- extremely important discoveries have the above investigators used the ABPP tion of this pulsar at Arecibo with the been made. First, statistical techniques and Princeton Mark IV backends. Their Princeton Mark IV backend. They find show that the radio emission from PSR data analysis includes a careful calibra- the pulsar to be very highly linearly po- B1937+21, the most rapidly spinning tion of the instrumental polarization, larized at this frequency, as shown in Fig. known pulsar, has no intrinsic pulse-to- which they verify by comparing the re- 9, implying that the previous non-detec- pulse fluctuations at 430 MHz aside from sults for a sub-set of sources with results tion of polarization by Zepka et al. was the already known “giant pulses” which from both systems. Fig. 8 shows the ex- a result of Faraday depolarization across occur in a restricted region of pulse ample of the integrated full-polarization their observing bandwidth. They obtain phase. Such a phenomena has never be- pulse profile for PSR J2317+1439 at 430 a rotation measure of 317±27 rad m-2, fore been observed. The techniques de- MHz measured with Mark IV. A detailed implying a mean interstellar magnetic veloped to analyze these data show that analysis of the physical implication of field along the line of sight of ~3 µG, a it is possible to study the pulse-to-pulse the results is under way. reasonable value for the Galactic anti- properties of low signal-to-noise pulsars. center direction. Fernando Camilo (Columbia), Dav- Since only a handful of pulsars are bright id Nice, Eric Splaver (Princeton), Zaven High time-resolution observations of enough to be seen above the noise lev- Arzoumanian (GSFC), Andrew Lyne radio pulsar emission have been per- els of currently available instruments, (Jodrell Bank) & Jim Cordes (Cornell) formed by Rick Jenet, Stuart Anderson, these techniques open up a window to have been monitoring the remarkable and Tom Prince (Caltech) using the the single pulse phenomenology of ten radio pulsar J0631+1037. This object Caltech Baseband Recorder (CBR). The to hundred times more objects. These was discovered at Arecibo in 1993 (Zep- main goal of these observations is to un- results and the analysis techniques are ka et al. 1996, ApJ, 456, 305) in a search derstand the nature of the pulsar radio described in a paper to appear in the De- of X-ray sources. The pulsar is relative- emission mechanism, a phenomena cember 2000 issue of the Astrophysical ly young (its characteristic age is 43,000 whose explanation has eluded research- Journal. yr) and exhibits unusual pulse profile ers since the discovery of radio pulsars The second discovery by Rick, Stu- structure. Camilo et al. have been mon- over 30 years ago. Two interesting and art & Tom concerns the nature of the

August 2000, Number 30 8 NAIC/AO Newsletter emission pro- it, at least an order of magnitude below cesses. Hence, the column density at which the outer these results edges of spiral galaxies are sharply trun- provide strong cated by extragalactic UV. At the reso- constraints on lution of the 3.2-arcmin beamwidth, the the emission outer edges appear to be smooth. If cor- process and re- rugation is to reconcile the low column quire the devel- densities reached with the expectation opment of that the external UV radiation field detailed theoret- should truncate the neutral fraction, the ical models irregularities must be considerably which may in- smaller than the beamwidth. clude both gen- The non-Compact HVC was found eration and to have a satellite superimposed on its propagation of northern edge, differing in velocity by the intense radi- about 60 kms-1, which is slightly more ation field in or- than twice the profile width of either the der to fully main cloud or its satellite. The satellite understand the was found to be 10 arcmin or so in di- observations. ameter with a peak column density of a Both the analy- few ×1018 atoms cm-2. That column den- sis techniques sity is an order of magnitude smaller than and these results the central column density of a typical are described in HVC, and is smaller than the central a paper recently Fig. 9: The full-polarization integrated pulse profile for PSR J0631+1037 at 430 column density of any other known submitted to the MHz. The measurements were made with the Princeton Mark IV. In the top frame, HVC. Neither the main cloud nor the Astrophysical the solid line is total intensity and the dashed line linear intensity, while the the satellite display any significant gradient lower frame represents the position angle of the linear polarization. (Courtesy Journal. Fernando Camilo) in velocity, in contrast to the CHVC which shows a rotation (or shear) differ- HI in High ence of 17 kms-1 (comparable to the pro- basic plasma emission process occurring Velocity Clouds (HVCs) file width at any individual position) in the pulsar magnetosphere. Using a Lyle Hoffman (Lafayette), with between the NE edge and the center. newly developed statistical tool specifi- Lafayette College student assistants cally designed to detect temporally co- Ryan Gildea and Mike Poccesci, has Zeeman Effect Studies herent, non-Gaussian field statistics, it made deep and detailed maps of the out- Dick Crutcher (Illinois) and Tom Tro- has been shown that the low frequency er edges of two High Velocity Clouds land (Kentucky) have observed the Zee- (i.e. 430-MHz) radiation from the pul- (HVC). One cloud is from Braun and man effect in the 1665- and 1667-MHz sars B0823+26, B0950+08, and Burton’s list of Compact High Velocity lines of OH towards eight dark cloud B1133+16 are not consistent with the Clouds (CHVC), the other being one of cores. For L1544 the inferred line-of- standard amplitude modulated noise the smallest HVC from Wakker’s com- mode. The results show that the emis- sight magnetic field is B = +11±2 µG. pilation not to be included in the list of los The L1544 starless core has been ob- sion statistics are clearly non-Gaussian CHVC. At the outermost positions, in- served to have in-fall motions; it may be and temporally coherent. Various basic tegration times were sufficient to give physical parameters related to the plas- very close to forming a star. B ~ 11 rms flux densities around 0.5 mJy, for a los µG is consistent with the prediction of ma environment may be estimated from minimum detectable column density a an ambipolar diffusion model comput- the data, but these estimates will remain bit less than 1018 atoms cm-2. Sidelobe ed specifically for this core before the highly uncertain until the effects of in- contributions (from the first sidelobe Zeeman measurements were made; how- terstellar medium (ISM) propagation and ring) to the outer points were estimated ever, in order to obtain agreement with signal digitization on non-Gaussian sig- to be about 20% of the observed flux the data, this model has B inclined by nals are better understood. Thanks to the density, easily corrected for in an approx- only 16° to the plane of the sky. Virial detection of non-Gaussian statistics, the- imate fashion. The column density in arguments show that unless the magnet- oretical models can no longer rely on the each cloud was found to decline essen- ic field is mainly in the plane of the sky, central limit theorem to average away the tially exponentially to our sensitivity lim- collective effects of the basic plasma it is not important for support of the

August 2000, Number 30 9 NAIC/AO Newsletter L1544 core. For L1457S, they find Blos The result for 3C18, which has one mally unstable regime violates a funda- = −24±7 µG, a possible, but not definite, of the simplest profiles and is good as mental cornerstone of equilibrium ISM detection. The other six cores were only an illustrative example, is shown in Fig. models (McKee & Ostriker, 1977, ApJ, observed with short integration times, 10. The solid line in Fig. 10A is the ob- 218, 148; Field, Goldsmith & Habing, and the Zeeman effect was not detected served absorption spectrum, fitted with 1966, ApJ, 155, L149), which all rely on in these. three CNM components, whose depths stable thermal pressure equilibrium to and halfwidths are indicated; the dash- push the gas into one of the thermally Carl Heiles (Berkeley) & Tom Tro- dot line is the fit, which is almost indis- stable CNM or WNM phases. Signifi- land (Kentucky) are in the midst of a tinguishable from the data. Fig. 10C is cant amounts of gas in the thermally un- extensive program to observe Zeeman the emission spectrum. The solid line is stable regime is a problem for such splitting of the λ21-cm HI line in absorp- the data, fitted with (1) the amplitudes models and pushes one towards time-de- tion against bright radio sources. Fasci- of the three absorption Gaussians, keep- pendent models such as Gerola, Kafatos nating as the magnetic field results are ing their centers and widths fixed; plus & McCray (1974, ApJ, 189, 55). proving to be, a new by-product is em- (2) a single WNM component. The phasized here; new absorption/emission dashed curve is the contribution from the results to derive the spin temperatures, The ensemble of CNM Temperatures: WNM component, which is unabsorbed in the spirit of the classical Arecibo work T in the three 3C18 CNM components by the CNM because all the WNM is s by Dickey, Salpeter & Terzian (1978, are (from left to right in Fig. 10A) 46±9, taken as lying in front of the CNM, pro- ApJS, 36, 199: DST), and Payne, Sal- viding the lowest re- peter & Terzian (1982, ApJS, 48, 199: siduals. The sum of PST). It is first mentioned that about half the full fit (shown as of the DST absorption profiles exhibit a dash-dotted line) is large differences from the new measure- a good fit. ments, the DST components being wid- er and multiply-peaked. Apparently DST The ensemble of had local-oscillator stability problems WNM Tempera- (John Dickey, private communication). tures: The single However, the more important thing is the WNM component of new interpretation of the data, which dif- 3C18 has FWHM of fers in one important detail from previ- 10.0 kms-1, corre- ous ones. The absorption spectra consist sponding to purely of very obvious velocity components thermal broadening and, like DST and PST and other authors, at T=2200 K, setting Carl & Tom represent their optical depths an upper limit on the by Gaussians. Unlike previous authors kinetic temperature. is the treatment of the associated emis- For the ensemble of sion spectra, because it is physically self- WNM Gaussians, consistent. They decompose the about half have Ts < emission profile into two sets of Gauss- 5000 K; as these ians: (1) a set with the same centers and components are not widths as the absorption-profile Gauss- visible in absorption, ians, with fitted amplitudes; and (2) one their spin tempera- or two additional Gaussians to make up tures are Ts > 500 K. the difference. The former set is the Cold The range 500-5000 Neutral Medium (CNM) and the latter K is the thermally the Warm Neutral Medium (WNM). unstable range that Interesting details include considering separates CNM from the fraction of WNM that lies in front of WNM, and these λ the CNM and, also, the relative order- data show this depar- Fig. 10: A and B exhibit the 21-cm line absorption Stokes I and V towards 3C18. In A, the solid line is data and the dash-dot line the fit; ing along the line of sight of the CNM ture from thermal crosses indicate Gaussian component parameters. In B, the solid line components — nearby ones absorb the stability in a statisti- is data, the dash-dot line the Zeeman-splitting fit, and the dashed line more distant ones. For most sources, the cally convincing the Stokes I spectrum. C is the emission Stokes I; the solid line is the CNM components plus one or two manner. The appar- data, the dashed line the contribution from the three CNM components, WNM components produce very good ent preponderance of and the dotted line the WNM component. (Courtesy Carl Heiles) fits to the emission profile. WNM in the ther-

August 2000, Number 30 10 NAIC/AO Newsletter 43±6, 32±1 K. These values are repre- ing strong fields (with large errors), is Molecular-Line Studies sentative of the ensemble of CNM Gaus- common in Carl & Tom’s sample and Murray Lewis (NAIC) and the 1998

sians, with most having Ts < 75 K, in may be statistically valid. The large er- Arecibo summer students began one of marked contrast to previous results; for rors occur because the components are the first projects to use the new auto-cor- example, DST & PST found histograms weak and wide, but can be reduced with relation spectrometer in taking introduc- with broad peaks over the range 50-300 more observing time, a future priority. tory OH-line spectra of 10 Arecibo OH/ K. The present range is narrower, with a The results for the third Gaussian, which IR stars. They found that the peak 1612- suggestion that the distribution is dou- is the strongest and is fairly narrow, MHz intensity of one of these, bly peaked, with peaks in the ranges 10- might also be significant. If so, 3C18 18455+0448, had faded by a factor of 20 and 30-75 K. The 30-75 K range would be unusual in having a probable 20 from its 1988 discovery intensity of agrees well with the standard theoreti- detection as strong as 3.7 µG for the 2.05 Jy, whereas a factor of 3 to ~10 cal model of Wolfire et al. (1995, ApJ, strongest component, as most sources change is normal for pulsation-related µ 443, 152). However, the 10-20 K range have Blos < 3.0 G for the strongest Gaus- changes. Indeed, subsequent observa- does not. Nevertheless, the theoretical in- sian with comparable or smaller errors. tions show that the maser has now faded terpretation of such low temperatures is These weak fields in the strongest by a further factor of 10, as shown in actually quite straightforward. When Fig. 11, where the 1988 observation is CNM components are surprising, being Spitzer (1978) wrote his famous text- lower than the volume-average field placed at the illustrative position it would book, heating by photoelectric emission have if the exponential decline had con- strength of about 5 µG derived from var- from dust grains was not a well-accept- ious data independently by Heiles (1996, tinued over the whole dataset. The 303- ed process, and he calculated the CNM day e-folding time for the maser implies ASP conf. Ser. 97, 457) and Ferriére equilibrium temperature assuming that (1998, ApJ, 497, 759). This volume-av- that its total decline may require little only the classical mechanisms prevailed, more than four years. Moreover, since eraged field is characterized by very namely heating due to photoionization small volume densities, much smaller correlations between the expansion ve- of Carbon and cooling by electron re- locity and period of OH/IR stars suggest than the n ~ 100 cm-3 of CNM clouds. combination onto ionized Carbon. The HI With flux freezing, field strength should a likely period of ~400 days for equilibrium temperature is 16 K, inde- 18455+0448, we can be sure that the increase with volume density. The idea pendent of the Carbon abundance and the that the CNM should have high field decline in the 1612-MHz maser is per- starlight intensity. For CNM gas not to manent, even though its mainline OH strengths is observationally confirmed be heated by photoelectric emission from by the ~10 µG fields observed in HI masers are still unaffected. These chang- grains, the gas cannot contain grains — emission lines coming from morpholog- es are expected if we are witnessing the more specifically, the gas cannot contain ically obvious superbubble walls (Heiles, last stages in the expansion of a fossil the particular kinds of grains that heat 1989, ApJ, 336, 808) and other structures shell of OH molecules around the gas. In Wolfire et al.’s theory, these (Myers et al., 1995, ApJ, 442, 177). Note 18455+0448, before it evolves into a are small grains (>400 A) and PAH’s. It the critical difference between those re- planetary nebula. This identification as seems difficult to produce gas without sults and the current ones: those were for a proto-planetary nebula is also support- such grains. One cannot rely on strong line of sight chosen specifically because ed by its red IR colors, and the absence shocks, because they add to the small- they contain morphologically obvious of both water and SiO masers. It will be grain population by shattering large structures and fairly large column den- interesting to find out for how long it will grains (Jones, Tielens & Hollenbach, sities, while the current sightlines require 1996, ApJ, 469, 740). It seems that one the presence of suitable extraga- must destroy all the grains, perhaps by lactic radio sources and are thus cycling the gas through the hot million- 8.0 randomly chosen. What is sur- ( ) 1988 degree phase, or let the CNM cloud sit decline in 1612 MHz maser 7.0 prising is that these randomly- 18455+0448 quiescently for a long time so that small chosen CNM components, with 6.0 grains coagulate into large ones.

fairly large volume densities (mJy) 5.0 1998.6 1612 Zeeman splitting of the CNM compo- (but small column densities), 4.0 ln I nents: Fig. 10B exhibits the Stokes V have smaller field strengths than 3.0 spectrum for 3C18, together with the typical regions of the ISM, 2.0 ± -1000.0 -500.0 0.0 500.0 1000.0 least-squares fit yielding Blos=(0.2 11.8, which have much smaller col- 18.2±5.7, -3.7±1.6) µG. The result for umn densities. time (days from 1998.0) the second Gaussian would be exciting if significant because it is the widest component with a strong field. This Fig. 11: The “light curve” of the peak 1612-MHz intensity of 18455+0448. (Courtesy Murray Lewis) combination, the wide components hav-

August 2000, Number 30 11 NAIC/AO Newsletter mum circa 25 Jy over com- izations, and processes data in near real- V1511 Cyg (19586+3637) ing years or decades, while time using a three-stage pipeline. Daily establishing just how much observations of the Pioneer-10 spacecraft 300 1612 MHz of this increase is exponen- test the entire signal processing system 200 tial. This will, in turn, pro- and the two-antenna, pseudo-interferom-

100 vide strong, and thus far etry signal confirmation technique. More Flux ( mJy ) unique, observational con- than 270,000 signals were detected dur- 0 -20 0 2 0 4 0 straints on models of masing ing these observations. So far, no clear- LSR Velocity ( km/sec ) shells. Arecibo is particular- ly extraterrestrial transmissions have ly well placed to witness the been found. Fig. 12: The 1612-MHz, OH-maser emission spectrum births of more OH/IR stars. of 19586+3637, (alias V1511 Cyg = IRC+40371), on 29 This is needed both to estab- SKA Meeting - February 28-29, 2000 May 1999. The star then exhibited a 332-mJy maser where lish V1511 Cyg as the pro- none had been visible 8 yr earlier, making it a “mimic” totype, and to establish the Yervant Terzian and Mike Davis that has recently become an OH/IR star. (Courtesy Murray Lewis) generality of its accompany- he US Square Kilometer Array Con- ing circumstances, which Tsortium invited all interested astron- included several hundred omers to an open meeting to discuss the years as a mimic without any US participation in the international be possible to follow the decline of all masers. project to construct a ‘Square Kilometer of the OH masers. Array’ radio telescope. These meetings took place at the Arecibo Observatory on An inventory of high-latitude (|b| > Search for Extraterrestrial Intelli- February 28 and 29, 2000 and were at- 10°) circumstellar shells in the Arecibo gence sky with IR colors appropriate for OH/ tended by approximately 75 scientists. Under a long-term commitment, Project Jackie Hewitt (MIT) and Don Backer IR stars shows that up to 75% of them Phoenix of the SETI Institute made its do not exhibit 1612-MHz masers: indeed (Berkeley) introduced the project and third and fourth post-upgrade runs at discussed its scientific necessity. Discus- two thirds of these OH/IR star color Arecibo in Nov/Dec 1999 and Feb/Mar mimics do not exhibit mainline OH or sions during the first day concentrated 2000. These sessions continue their on- on the various new science that could be 22-GHz water masers either, whereas going search for extraterrestrial intelli- more than 90% of the OH/IR stars do. achieved with the SKA, such as in the gence signals from a large number of areas of pulsars, galactic and extragalac- However, OH/IR stars evolve into pro- nearby solar-type stars. The SETI Insti- to-planetary nebulae (PPN) at the cessa- tic astronomy, radar astronomy of the tute team make these observations us- solar system, SETI, and cosmology. tion of mass-loss, so it is significant that ing both the 305-m telescope and the only one of the sample’s O-rich PPN Clearly fundamental new science is ex- 76-m Lovell Telescope at Jodrell Bank, pected with the SKA. lacks any masers, where about 8 are ex- England, the present sessions being al- pected if mimics evolve directly into most trouble free at both ends. The start- This ambitious, new project has the PPN. Inferentially, therefore, most of up procedures, which gave software promise to chart a complete history of these mimics evolve into OH/IR stars be- problems during the run of early 1999, time of the universe. It demands a fre- fore becoming PPN. In this view, the im- now worked essentially without fault. quency coverage from about 100 MHz mediate precursor of an OH/IR star is Also working well was a new approach to 30 GHz, with a sensitivity at least 100 thus a mimic. This conclusion is direct- to dealing with persistent radio frequen- times that of the VLA. Such an instru- ly confirmed for V1511 Cyg (alias cy interference (RFI). Frequencies that ment will have a resolution better than 19586+3637) by recent Arecibo 1612- are unusable due to RFI are identified the Hubble Space Telescope and a field MHz observations by Murray, which early in a run, and are now circumvent- of view larger than the Moon. It would show that between 1991 and 1999 it be- ed in the search. This results in the skip- rival and complement the NGST. came an OH/IR star. While four obser- ping of about 30\% of the spectrum The second day of the meetings con- vations made at Arecibo and Nancay between 1200 and 1750 MHz. While the centrated on the SKA instrumentation between 1986 and 1991 provide a 56- loss of data is regrettable, this procedure and techniques. To achieve the required mJy upper limit on the presence of a allows the search of usable regions in capabilities of the proposed SKA, new 1612-MHz maser, V1511 Cyg now ex- the spectrum to proceed much faster. hibits a classic double-peaked profile technologies must be developed in the that had an easily detected 332-mJy peak During the two runs, more than 2,500 areas of array configurations, feeds, intensity in May 1999 (Fig. 12). It will observations of stars were made. Each frontends, correlators, etc. These issues be exciting to watch the maser progres- observation covers 20 MHz with 28.7 were addressed by Colin Lonsdale (Hay- sively strengthen to an eventual maxi- million channels in each of two polar- stack/MIT), Sandy Weinreb (JPL/

August 2000, Number 30 12 NAIC/AO Newsletter Caltech), Steve Ellingson (Ohio State), oxygen and metastable He emissions, main talks and discussions took place Jack Welch (Berkeley) and others. SKA discrepancies in different groups Hα in- over the following 2 days and, in all, 29 software and AIPS++ applications were tensity variations, ionospheric modeling presentations were given. Topics dis- also discussed by Tony Beasley (NRAO) and validity of empirical (MSIS and IRI) cussed included: pulsar searching at and Mark Holdaway (NRAO). models. Arecibo—Wolszczan et al. (Penn State), McLaughlin et al. (Cornell) and Lorim- Logistical aspects of the SKA, such One productive aspect of the work- er/Xilouris (NAIC), Parkes—Kaspi as where to build it and how to finance shop was that ample time was allowed (MIT), Camilo (Columbia) et al., and it, were addressed by Yervant Terzian for smaller subgroups to get together and other observatories; recent single-pulse (Cornell/NAIC), and Mike Davis discuss issues that may not have been observations conducted at Arecibo— (Arecibo/NAIC), respectively. The last easily discussed in a larger plenary ses- Jenet (CalTech) et al., and by an Indo- meeting session was chaired by Ken sion. In general there was unanimous European collaboration—Bhat (NAIC), Kellermann (NRAO) who spoke enthu- agreement that the workshop had been Karastergiou (MPIfR) et al.; reviews of siastically about the project. Bernie been a productive experience for the par- current instrumentation at the Observa- Burke (MIT) in his concluding remarks ticipants and we expect to hold a follow tory; discussions about what current and emphasized the crucial scientific contri- up workshop in the second half of 2001. future users require to optimize their use butions that the SKA could make in our In addition, we will soon be announcing of telescope time; progress reports from understanding of the structure and evo- a workshop to explore the new era of ob- other observatories (Green Bank, Effels- lution of the Universe and prompted all serving the ionosphere at Arecibo using berg, Parkes and the VLA), as well as of us to ‘Get To Work’. the dual beam 430 MHz radar and most pulsar timing results from around the likely will organize it using a similar Proceedings of the meeting are available world. format to the one that worked so well at: http://www.usska.org or on diskette for the topside workshop. More infor- In addition to current work, the need from Tony Acevedo [email protected]. mation about the topside workshop will to look ahead to the future of pulsar appear shortly on the web page of the searching and VLBI observations utiliz- space and atmospheric sciences group. ing the upgraded capabilities of the Arecibo Topside Workshop, March 6-7, 2000 Arecibo telescope was addressed by talks from Jim Cordes and Shami Chatterjee Sixto González Pulsars at Arecibo - A Y2K Work- (both Cornell). It is hoped that Arecibo his March saw the first Arecibo top- shop March 12-14, 2000 will play a key role in the discovery of Tside workshop at the Visitor Cen- Duncan Lorimer pulsars in the near future. ter. The organizers were Bob Kerr (Sci- ome 26 visiting scientists from the Following Cordes’ presentation on entific Solutions, Inc.), Phil Erickson USA, Europe and India attended a searching, the workshop participants (Millstone Hill) and Sixto González S Pulsar Workshop organized with much strongly urged the development of a 21- (Arecibo). In the true spirit of CEDAR help from Edith Alvarez at the Obser- cm multi-beam receiver at Arecibo we had a good combination of model- vatory on March 12-14. The aim of the which could be used to find many hun- ing, radar, and optical specialists in at- meeting was to bring together pulsar ob- dreds of young pulsars close to the Ga- tendance; in total there were around 25 servers to coordinate joint projects be- lactic plane in a large-scale survey. Such participants. The complete list can be ing undertaken and planned at the a system would have even greater sensi- found at http://www.naic.edu/~sixto/ Arecibo Observatory, as well as to tivity than the current system at Parkes attendees.html. present recent results from Arecibo ob- which has now found well over 500 pul- The primary objective of this work- servations, and from other radio obser- sars. In the second presentation, Chat- shop was to resolve some of the issues vatories. The meeting made use of the terjee reviewed the excellent potential and controversies in the general areas of excellent facilities now available in the for future high-precision astrometric ionosphere, plasmasphere, thermosphere observatory visitor center auditorium measurements to determine pulsar prop- and exosphere coupling by providing an where the chipper young lad José Alon- er motions and parallaxes. Pulsar VLBI informal forum that allowed and encour- so and his staff provided the perfect at- will begin in the near future once the aged more direct interaction. The obser- mosphere to conduct the meeting. MkIV recorder is installed at the Obser- vatory provided an ideal setting for this During the first day, participants vatory. and in general we achieved the goal of gathered at the Observatory to hold small Although there are no formal pro- generating good discussion and avoid- group discussion meetings on pulsar tim- ceedings from this meeting, almost all ing formal (‘AGU style’) talks. We had ing and, for newcomers, tours of the fa- of the speakers have subsequently made extensive discussions on issues as di- cilities were given by Chris Salter. The their presentation materials available and verse as the effect of photoelectrons on

August 2000, Number 30 13 NAIC/AO Newsletter these have been posted on the meeting 19 June, Murray Lewis (NAIC) OH/IR 100 channels. This correlator could web page: http://www.naic.edu/~pulsar/ Stars dump its data to a computer. (Weinreb’s y2kws to form a useful repository of the original correlator had electro-mechan- 21 June, Don Campbell (NAIC) Radio information that was exchanged during ical counters as final accumulators; the Astronomy Principles the meeting. The workshop was enjoyed experimenter used a clipboard and pen- by all concerned and it is hoped that, 22 June, Karen O’Neil (NAIC) An LSB cil to record the totals after each inte- with the advent of more on-site accom- Galaxy Primer gration cycle). modation, we can organize further pul- At the same time, Arecibo had a 50- sar gatherings at Arecibo at regular 27 June, Jean-Luc Margot (NAIC) Ra- channel 1-bit × 8-bit correlator for the intervals in the future. dar Astronomy Principles measurement of the incoherent scatter 6 July, Ramesh Bhat (NAIC) An Intro- spectrum. This unit used TTL chips, and Recent NAIC colloquium talks duction to Pulsar Astronomy around 1974 we built a TTL correlator Karen O’Neil and Duncan Lorimer 7 July, Duncan Lorimer (NAIC) Search- with 1008 channels for radio astronomy. ing for and timing radio pulsars This correlator had a 20-MHz clock rate n this new addition to the newsletter for 1-bit operation and a 10-MHz clock Iregular features, we list the 12 collo- 10 July, Daniel Altschuler (NAIC) rate for 3-level operation. quium talks and 13 summer student lec- Arecibo observatory: History and Sci- tures given since the last Newsletter ence The 1008-channel machine was re- appeared (March, 2000). Information on placed around 1984 with a clone of a new these and all upcoming talks at the ob- 12 July, Michael Nolan (NAIC) Aster- Berkeley correlator: 2048 channels and servatory can be found at: oids a maximum clock rate of 40-MHz with either 1-bit or 1.6-bit (3-level) operation. 12 July, R. Ganesan (RRI) Raman Insti- http://www.naic.edu/~astro/talks The Berkeley Correlator used the same tute Receivers at the GMRT 10 April, Tom Troland (Kentucky) Ap- TTL technology but achieved higher erture Synthesis Observations of the Ga- 13 July, R. Kraan-Kortewe (Guanajua- speed by virtue of better circuit design. lactic Magnetic Field to) Galaxies behind the Milky Way and The space factor was about the same: a the Great Attractor 6-ft rack held 1024 channels and each 12 May, Rob Swaters (Washington) Dark channel required about a half dozen in- 14 July, Richard Barvainis (NSF) Mo- matter in dwarf and LSB Galaxies tegrated circuits. lecular Gas and Dust in High Redshift 16 May, James Schombert (Oregon) The Galaxies Arecibo continued to use this 2048- Gas Fraction of Galaxies channel correlator into the 90’s, while 18 July, Ellen Howell (NAIC) Geology other observatories began building cor- 8 May, Lister Staveley-Smith (ATNF) of the Caribbean Plate relators based on a Dutch-designed semi- The HIPASS Multibeam Survey 19 July, Ramesh Bhat (NAIC) Probing custom gate array chip that held 16 19 May, John Salzer (Wesleyan) First the Local ISM using Pulsars channels. Around 1994, NAIC entered KISS - preliminary results from the into a collaboration with a NASA-spon- KPNO international spectroscopic sur- 21 July, Michael Sulzer (NAIC) Inco- sored VLSI design lab, then at the Uni- vey herent Scatter versity of Idaho and later at the University of New Mexico, that result- 22 May, Dick Manchester (ATNF) 47 26 July, Sixto González (NAIC) The Up- per Atmosphere ed in the design of a chip holding 1024 Tucanae - A Pulsar Goldmine 1.6-bit correlator channels with a clock 25 May, Trinh Xuan Thuan (UVA) rate of 100 MHz. The chips were fabri- Young blue compact dwarf galaxies and Peeps into the past: AO Correlators cated by Hewlett Packard and correla- the primordial helium abundance Jon Hagen tors with tens of thousands of channels have been built using these chips at he first correlator used for radio 1 June, Amy Lovell (FCRAO/Amherst) Arecibo, NRAO, and elsewhere. HCO+ in Comet Hale-Bopp: Amazing Tastronomy at Arecibo was a hand- data with a (somewhat) ordinary expla- me-down machine from the Haystack nation Observatory. This instrument, which ar- Comings and Goings rived around 1972, was an improved 16 June, Leo Blitz (Berkeley) High Ve- version of the 1-bit grandfather of all cor- Ramesh Bhat locity Clouds and the Formation and relators, built in the early sixties by Chris Salter Evolution of the Milky Way Sandy Weinreb. Built with discrete tran- This March we welcomed Ramesh Bhat sistors and housed in a 6ft. rack, it had to Arecibo Observatory as the Cornell

August 2000, Number 30 14 NAIC/AO Newsletter observers. His own research program ty of knowledge and observatory secrets with the 305-m telescope includes an from her past jobs at NRAO in Green extensive study of the scattering tails of Bank and Caltech’s Owens Valley Ra- distant pulsars, and an investigation of dio Observatory. Her specialty is micro- the interstellar scintillation properties of wave receivers. She will be a positive pulsars. We wish him well with these addition to our group. projects. With Snezana Stanimirovic, Ramesh has taken over organizing the Arecibo Journal Club, and is “Friend of the Receiver” for the new 327-MHz sys- tem, plus sharing this role with Tapasi Ghosh for the 430-MHz Gregorian re- Ramesh Bhat ceiver. This summer he supervised sum- mer student Amanda Kirschner from Carleton College in her project on the Post-Doctoral Research Associate in ra- secondary spectra of pulsar scintillations. dio astronomy. Ramesh hails from the Ramesh has settled down well in state of Kerala in India, and obtained his Arecibo, having already moved into his B.Tech. (Electronics & Communica- second apartment within 4 months! He tions) degree from the University of Ker- also impressed us all by surpassing even ala, Trivandrum, in 1992. That same Edgar Galloza Snezana’s achievements in “dealing” year, he joined the National Centre for with the Puerto Rican driving test. We Radio Astronomy (NCRA) in Pune, In- all welcome Ramesh to Arecibo, and Edgar Galloza: Edgar joins the elec- dia, being awarded his M.Sc. degree in trust that his stay with us will be happy, tronics department as an electronics tech- Physics by the University of Pune in fulfilling, and crammed full of exciting nician. He is assigned to the receiver 1996. Ramesh’s doctoral research work new experiences. group. He graduated from the Metro- was carried out using the Ooty Radio politan Technical Institute, U.S. Air Telescope (ORT). From the Electronics Department Force Training Command, Biloxi, Mis- With this instrument he completed a Edgar Castro sissippi. He has considerable experi- very extensive investigation of interstel- Lisa Wray: The electronics department ence, including having worked at the lar scattering effects on pulsar signals, is pleased to welcome its newest engi- U.S. Customs aviation branch, Raythe- particularly studying the electron densi- neer, Lisa Wray. We imported Lisa from on Aerospace, Honeywell, commercial ty fluctuation spectrum within the inter- her home and native land, Canada, where flight systems, Aguadilla radar, and stellar medium (ISM), and the ISM’s she earned a Bachelor’s degree in elec- Lajas Aerostat radar. He enjoys flying local structure. He became a shining ex- trical engineering from the University of airplanes. ample to us all by publishing most of his Alberta. Later, she completed a Mas- Alexis Echevarría González: On Au- Ph.D. research results even before receiv- ter’s degree from the University of Cape gust 10, 2000 Alexis began to work as a ing his doctoral degree in May 1999. Town, South Africa. Lisa brings a boun- regular employee at the Arecibo Obser- From August 1998, he spent a period as a Visiting Research Fellow at NCRA, passing much time with the newly com- Lisa Wray pleted Giant Metre-Wave Radio Tele- scope (GMRT) at Khodad where he worked on telescope commissioning and helping develop a pulsar presence at the new instrument. In the summer of 1999, his pulsar studies took him on extended visits to Jodrell Bank and Effelsberg. Since arriving at Arecibo, Ramesh has begun an active pulsar observing program, as well as contributing to en- suring the success of various absentee observing runs and friending visiting Alexis Echevarría González

August 2000, Number 30 15 NAIC/AO Newsletter vatory in the Electronics Department as her tenure at Arecibo (supported through Electronic Technician in communica- an EPSCoR project), Shikha will extend tions. He studied electronics in the Uni- and further refine our observational pro- versity of Puerto Rico (Aguadilla gram of atmospheric composition utiliz- Campus). As a summer student here in ing the differential absorption lidar 1999, he worked on the wideband-LAN systems recently developed at the Ob- installation. servatory. I am also told that her recent arrival adds a critical element to the suc- Francisco Nieves: After 33 years of cessful formation of a future Arecibo work at the Observatory, Frankie Nieves cricket team. (second from left in photo below) has decided to join our elite group of retir- ees. Frankie was responsible for all the A Few Things of General Interest communications at the Observatory. Daniel R. Altschuler When he started working here all the communication was done through a one Shikha Raizada telephone (linked to Ramey, AFB), one Remote Observing Protocol telex machine, and the long distance to Remote observing is being used by sev- Prior to that, she studied the coupled ion- Cornell through an HF transceiver. This eral groups, and we have started to de- neutral electrodynamic characteristics was a far cry from our present state-of- velop procedures to ensure proper and and various irregularities of the iono- the-art communications system! We safe use of the telescope. The current sphere, combining rocket-borne mea- want to wish Frankie our best. we will protocol is as follows: surements of electron concentration with miss you Frankie!! ground-based imaging of oxygen air- (1) The remote observer calls the con- glow emissions. trol room (+1-787-878-2612; Exten- Shikha Raizada sion 211 or 229) up to an hour in Craig Tepley At Arecibo, Shikha will work with our advance of the observing session to Dr. Shikha Raizada joined the Optical lidar and low altitude radar systems to obtain the current “dtusr” password Sciences Division of the Space and At- investigate the distribution, motion, and and to pass on any special requests mospheric Sciences Department at vertical coupling of aerosols and minor for setup in the observing room. Fail- Arecibo in August 2000. She hails from gas species between the stratosphere and ure to make contact with the opera- troposphere. One goal is to examine the Jaipur, India and recently worked at the tor within 15 minutes of the start of Indian Institute of Astrophysics in Ban- possible influence these constituents the run may result in a delayed start might have on regional weather patterns galore where she studied atmospheric to the observing run. turbulence as applied to the seeing prop- in the tropics, and the role they may play erties of large astronomical telescopes. in atmospheric climate change. During (2) Having obtained the password, the observer logs in and, when his/her alloted time on the telescope begins, starts the user interface by typing ei- ther “gui” for the graphical version (recommended) or “tui” for the low-bandwidth text-only version. This runs a script to get the remote ob- server’s name, project ID,contact telephone number and permission to observe from the operator. (3) Once permission has been given by the operator, the script will start the data Francisco Nieves, second from left, joins the elite group of Arecibo Observatory Electronics Department retirees. Here taking program and also ini- he is joined by retirees (from left to right) Domingo Albino, (Frankie), José López, Roberto Rojas, and Miguel Feyjoo. tiate a chat session between the operator and the observ-

August 2000, Number 30 16 NAIC/AO Newsletter er. The observer has full control of Proposal Information renovation, we hope you will be pleas- the telescope motion and turret posi- We have begun to publish information antly suprised the next time you visit. tion during this time, just as he/she about scheduled proposals. You will be would have observing from the con- able to obtain the title, abstract, and PI trol room. contact information for any project that Job Opportunities has been scheduled. You can sort the (4) On completion of the observing run, Vacant Research Associate Position the observer informs the operator that list by project ID number, or first author. This is available together with the tele- they are finished observing and are The National Astronomy and Ionosphere about to hand back control of the tele- scope schedules on our web site. Center (NAIC) anticipates having an scope. If the observer is still in con- opening for a radio astronomer at the Arecibo Observatory, which is located trol of the telescope AFTER his/her VSQ News allotted time without authorization, in the karst hills of the Caribbean island Our VSQ’s are being outfitted with com- the operator has the option to abort of Puerto Rico. puters attached to our LAN so that, in their data taking process. view of the limited space available, our The vacancy could be filled at the (5) It is expected that remote observers visitors have the option of working in level of staff Senior Research Associate be at their stations all the time, and the rooms, which have been renovated. or Research Associate, depending upon inform the control room about any We have developed plans for new the qualifications and experience of the changes in this condition. The oper- VSQ’s, to be able to host scientific and successful applicant. The Observatory is ator will establish contact with re- teacher workshops and house our sum- a National Center for research in radio mote observers every 15 minutes or mer students, and hope to find the nec- astronomy, planetary studies, and space as necessary, to ascertain that there essary funding to be able to begin and atmospheric sciences, accepting ob- are no problems. construction. They will be located on serving proposals from scientists world- new property acquired outside the gate wide. It is part of NAIC, which is of the obsevatory. Funds for the new operated by Cornell University under a Friends of the Receiver Learning Center have been obtained cooperative agreement with the Nation- The following members of the staff from the Angel Ramos Foundation, so al Science Foundation. The Arecibo 305- will act as Friends of the Receivers. that we might expand our very success- m reflecting telescope was recently ful science teacher training program. upgraded to include a Gregorian reflec- 327-MHz Gregorian: Ramesh Bhat Construction documents have been com- tor system and associated instrumenta- 430-MHz Carriage House: Duncan pleted and we expect to begin construc- tion permitting observations from 300 Lorimer tion in the near future. Along with the MHz to 10 GHz. In addition to the tele- scope’s low system noise and high gain, 430-MHz Gregorian: Tapasi Ghosh/ completion of the gazebo and cafeteria a wide range of state-of-the-art backends Ramesh Bhat 610-MHz: Tapasi Ghosh L-Narrow: Karen O’Neil L-Wide: Murray Lewis S-Radar: S-Band Radar Group S-Wide: Snezana Stanimirovic C-Band: Chris Salter They will act as contact points with users with respect to the performance and status of a receiver, keep this informa- tion up to date on our web page, keep track of RFI issues, monitor Tsys and manage and initiate calibrations as nec- essary.

The new cafeteria gazebo, part of the VSQ improvements (Photo by Tony Acevedo)

August 2000, Number 30 17 NAIC/AO Newsletter are also available allowing broad-band- academic, professional and personal hence eligible for all relevant Universi- width studies for spectral-line, pulsar, data, a research plan, and the names and ty benefits. Salary and benefits are com- continuum and VLBI research. contact information for at least three ref- petitive, attractive, and include a erences to: relocation allowance. Evaluation of ap- The successful candidate will have The Director, National Astronomy and plications will begin September 15, the opportunity to capitalize on these Ionosphere Center, Cornell University, 2000, although applications received lat- features. A stimulating research environ- Space Sciences Building, Ithaca, NY er than this may be considered. Please ment is provided by approximately 25 14853-6801. EOE/AAE. send a curriculum vita and names and resident staff scientists, postdoctoral fel- contact information of at least three ref- lows and senior engineers, as well as erences to: over 200 visiting scientists per year. In Vacant Digital Engineer Position addition, physics and engineering facul- The National Astronomy and Ionosphere ARECIBO OBSERVATORY ty and students of the University of Pu- HC 3 Box 53995 Center (NAIC) has an opening for a Dig- Arecibo, PR 00612 erto Rico have a cooperative research ital Engineer at the Arecibo Observato- Attn: Human Resources Department and educational association with the ry in Puerto Rico. The facility is an Observatory. All applicants whose re- NSF-funded National Center for re- NAIC and the Arecibo Observatory search interests include any field of ra- search in radio and radar astronomy, and are operated by Cornell University un- dio astronomy that can be exploited with in atmospheric science, accepting ob- der a cooperative agreement with the the Arecibo telescope will be considered serving proposals from scientists world- National Science Foundation. Cornell is for the position. We particularly encour- wide. The Arecibo 305-m telescope has an equal opportunity/affirmative action age applications from individuals who recently been upgraded with a Gregori- employer. are actively involved in radio molecu- an reflector system and instrumentation lar-line spectroscopy, a topic which is which will permit observations within a particularly pertinent to the improved frequency range spanning 300 MHz to high-frequency performance of the tele- 10 GHz. This upgrade has resulted in sig- scope. Besides conducting an indepen- nificant improvements in available band- dent research program, on-site staff widths, system noise, and gain. scientists are expected to advise visiting scientists in all aspects of their observa- The Arecibo Observatory is located tions, and to help define and implement in the karst hills of the beautiful Carib- improvements in equipment, observing bean island of Puerto Rico. A stimulat- procedures and data reduction. A PhD ing research environment is provided by in astronomy or a related field is re- resident staff scientists, over 200 visit- quired. ing scientists per year, and the engineer- ing and software professional staff. Staff Research Associates are ap- pointed for a three-year period and may NAIC seeks a person with experience be reappointed for an additional three working with digital signal processors, years, at which time promotion to Se- PLC programming, C programming, and nior Research Associate may be consid- possessing good interpersonal skills. ered. Senior Research Associates are Some experience with control systems appointed for a five-year period, with would be desirable. The successful can- reappointment after review. The success- didate will be responsible for the design, ful candidate will be an employee of development, implementation, and doc- Cornell University, and hence eligible for umentation of data taking and motion all University benefits. Salary and ben- control systems, as well as upgrading efits are competitive, attractive, and in- and problem solving for current systems. clude relocation allowances. Details will Requirements include a Masters degree depend upon the candidate’s qualifica- in electrical engineering, or equivalent, tions and experience. and a minimum of 3 years experience in the design, programming and implemen- Evaluation of applications will begin tation of digital electronics hardware. 1 November 2000, although applications received later than this may be consid- The successful candidate will be an ered. Please send a complete resumé of employee of Cornell University, and

August 2000, Number 30 18 NAIC/AO Newsletter

TO:

*address correction requested correction *address

Ithaca, NY 14853-6801 U.S.A. 14853-6801 NY Ithaca,

Cornell University Cornell

504 Space Science Building Science Space 504 NAIC/Arecibo Observatory Newsletter Observatory NAIC/Arecibo

NAIC/AO Newsletter is published three times per year by the National Astronomy and Ionosphere Center. The NAIC is operated by Cornell University under a cooperative agreement with the National Science Foundation.

Duncan Lorimer and Jonathan Friedman, Editors

Address: NAIC/AO Newsletter HC03 Box 53995 Arecibo, PR 00612 Phone: +1-787-878-2612 Fax: +1-787-878-1861 E-mail: [email protected] or [email protected] WWW: http://www.naic.edu